This invention concerns the structure of a fishing sinker. In order to make a fishing bait immersed down in the water and kept at a fixed depth, a sinker with a proper weight is needed to be fastened to the fishing line to enable the bait to roam within a proper limited range, especially where water flows rather rapidly. However, the sinker sometimes will drop on a craggy surface of a rock and be stuck in a gap so that the fishing line can not be pulled back unless it is cut off to discard the sinker.